WHAT THE BODY IS MADE OF 



93 



mentioned are known as chemical elements. The first four 

 named, oxygen, carbon, hydrogen, and nitrogen, are the ones 

 which are of most interest to us just now, as they form the 

 bulk of most foods. Carbon, oxygen, hydrogen, and nitrogen, 

 for example, come to us in such 

 foods as meats and vegetables. 

 Water supplies much of the hy- 

 drogen and oxygen. One ex- 

 periment which can easily be 

 performed at home will show 

 some of the elements contained 

 in foods. 



Experiment. To show presence of car- 

 bon and water in foods. 



Materials: Several foods, as potatoes, 

 meats, oatmeal. A metal plate or 

 small piece of sheet metal. Burner. 

 Glass funnel. Sugar. Sulphuric 

 acid. A 500 cc. beaker. 



Method and Results: Place a small 

 piece of the food to be tested upon 

 the metal and heat it. Hold the 

 glass funnel over it as a test for 

 escaping moisture. Continue heat- 

 ing until a black residue is left. 

 What in all probability is this black 

 substance ? 



Strong sulphuric acid has such attraction for water that it will withdraw 

 the water from many plant products and generate enough heat to sepa- 

 rate it from the black carbon. This is very strikingly done with sugar. 

 Mix 60 grams of sugar in 45 cc. of water in a 5oo-cc. beaker which is 

 set on a plate. Pour 60 cc. concentrated sulphuric acid into the sugar 

 solution. Result ? (If performed as an individual pupil experiment use 

 one fourth quantities suggested.) Can you name the black product? 



Some of these chemical elements, although present in 

 very small quantities, have extremely important uses ; 



Chart to show the percentage of 

 chemical elements in the human 

 body. 



